The technical field of the invention is that of needleless syringes intended to inject solid, liquid or mixed particles of active principle through the skin for therapeutic use.
Specifically, the invention relates to a needleless syringe operating on the basis of an initiating device involving a triggering device associated with a pyrotechnic charge. More especially, this triggering device is to be suited to the firing of a pyrotechnic charge housed in a lightweight small sized object and which has to be actuated manually.
The solution proposed by the invention recommends the use of a friction igniter as a main part of the triggering device for triggering the needleless syringe.
It would seem that, in the field of needleless syringes, there is no patent relating to the use of a friction igniter in the triggering device of such syringes. However, other types of triggering device have already been developed for needleless syringes involving a pyrotechnic charge. Mention may, for example, be made of U.S. Pat. No. 2,322,244 relating to a needleless hypodermic injector operating on the basis of a blank cartridge, the firing of which is brought about by the percussion of a piston brought up to speed by the relaxation of a spring, this firing being triggered manually by first of all contracting the said spring using a button. The liquid to be injected which is in contact with the cartridge is expelled from the injector under the effect of the pressure generated by the combustion gases. U.S. Pat. No. 4,089,334, for its part, describes a needleless injector equipped with a pyrotechnic charge, the firing of which is brought about by a primary charge, itself initiated by percussion of a rigid rod set in motion by the relaxation of a spring. The gases emitted by the pyrotechnic charge expand in a downstream chamber, setting in motion a piston whose movement causes the liquid product that is to be injected to be expelled. These two patents tend to show that percussion triggering devices involving, in particular, a spring, a solid component acting as striker and at least one pyrotechnic charge, are well known in the field of needleless syringes.
Finally, it is beneficial to mention U.S. Pat. No. 3,145,712 which relates to a device for the transcutaneous injection of medicinal product intended at supplementing suits that provide protection against gas attack. These devices are carried by the individual and can be triggered either manually or automatically if gas is detected. These devices operate on the basis of a pyrotechnic cartridge fired by a primary charge, this being initiated electrically by a current created between two carefully located terminals within this primary charge. The gases generated by the combustion of the pyrotechnic charge create a pressure which serves to eject the liquid medicinal product.
By contrast, the use of a friction igniter for initiating a pyrotechnic charge in objects such as, for example, flares, grenades or mines, is known and has been the subject of numerous patents. Mention may, among others, be made of French Patent FR 2 393 261 which relates to an undetectable mine for tracked vehicles which can be triggered by a friction wiper whose movement in contact with a detonator will contribute to its initiation.
Likewise, French Patent FR 2 487 968 describes an igniter cap particularly suited to the firing of grenades and containing, in particular, an ignition pyrotechnic chain the first element of which is a pyrotechnic charge which can be initiated by friction.
Needleless syringes need to be endowed with a triggering device which can be actuated manually and which makes it possible to dispense with an excessively energetic or bulky activation source while at the same time remaining reliable and performing well. In effect, the customary triggering devices used involve detonators whose primary composition is particularly sensitive. In storage situations, these syringes may therefore carry a risk of inadvertent operation, because of the high sensitivity of the detonator to external influences such as high temperatures or droppage. Furthermore, in spite of their sensitivity, the detonators, to be initiated, require a relatively bulky percussion device. In order to solve this bulk problem and this risk of inadvertent operation, it has been discovered that it is possible to miniaturize a friction initiator, achieved with good safety, and which triggers with excellent reliability. This friction initiation occurs gently, by directly igniting the pyrotechnic charge, without having to resort to a shock wave as was the case in initiation with a detonator. This has, as a direct and advantageous consequence, the effect that the noise produced when using the syringe is extremely limited. Finally, the needleless syringe according to the invention, having a friction triggering device, has a double safety feature; one of the features is in the form of a retractable component preventing any depression of the trigger and the other is in the form of an area of roughness requiring particular effort to depress the trigger once the retractable component has been removed.
The needleless syringe according to the invention has all these technical characteristics which are particularly well suited to needleless injection.
The subject of the present invention is a needleless syringe equipped with an initiating device comprising a triggering device and a pyrotechnic charge, characterized in that the triggering device comprises a triggering member connected to a friction means of the pyrotechnic charge. The friction means consists of a component whose main function is to rub against a pyrotechnic charge with the purpose of directly initiating it. A device such as this requires a friction-sensitive pyrotechnic composition such as zirconium-based compositions, for example. Advantageously, the friction means is a friction igniter. As a preference, the friction igniter consists of an elongate component one end of which has asperities. As a preference, the component is rigid and has an approximately cylindrical shape. Advantageously, the component is secured to the triggering member so that its movement is dictated by the movement imparted to the said member.
According to one preferred embodiment of the invention, the triggering member is a push-button intended to be actuated manually and capable of sliding along an elongate hollow central body in which the pyrotechnic charge is housed. In the xe2x80x9cstoragexe2x80x9d configuration for which the needleless syringe has not yet operated, the friction igniter is distant from the pyrotechnic charge. This charge will be ignited when the friction igniter comes into contact with it, giving rise to direct mechanical friction.
As a preference, the push-button is placed at one of the ends of the central body to make it easier to actuate, and more especially is placed at the opposite end to the end via which the active principle is injected. Advantageously, the friction igniter and the pyrotechnic charge are aligned along the axis of the hollow body. As a preference, the friction igniter and the pyrotechnic charge have a roughly cylindrical shape and their axis is coincident with the axis of the hollow body. Advantageously, an area of roughness located between the push-button and the central body makes it possible to increase the friction forces between the two elements as one slides along the other. In more concrete terms, this area allows the introduction of resistance preventing any initiation so long as sufficient effort is not applied for sufficiently long to depress the friction igniter and bring it into contact with the pyrotechnic charge.
As a preference, the area of roughness consists of the fitting-together of annular asperities of one of the two elements into grooves in the other element which are designed to accommodate them, so as to entail a minimum level of pressure required to begin to depress the push-button. This avoids inadvertent triggering as a result of mild or unintentional stressing when the needleless syringe is rendered operational by removing the retractable stop which protects the end via which the active principle is injected.
Specifically, and as a preference, the push-button has a safety feature in the form of a retractable stop preventing any movement of the said button. The other function of this safety feature is to protect the end of the syringe from which the active principle is to be ejected.
Advantageously, the retractable stop consists of a cap equipped with a collar immobilizing the push-button. A circular line of weakness allows the collar to be detached from the cap. The collar is rigid and has a tag for tearing it. Advantageously, the annular asperities constituting the area of roughness have the particular feature of preferably deforming along the axis of thrust and of therefore having a non-return effect. Thus, the user does not run the risk of being subjected to the effects of the abrupt retreat of the push-button. As a preference, the friction igniter is made of stainless steel.
Needleless syringes according to the invention have the advantage of producing a pyrotechnic reaction which is not as violent as the reaction perceived during operation of a percussion detonator. This is because they allow the gas-generating composition to be initiated gently by friction rather than via a shock wave.
In addition, as they are triggered and as they operate, they give rise to an extremely limited amount of noise.
Finally, they have the advantage of being placed on the civilian market without being subject to the constraints inherent to devices involving explosives or detonating compositions.